Novel phase change magnetic material

ABSTRACT

The invention relates to a phase change magnetic composite material for use in an information recording medium, said material comprising a phase change material component, and a ferromagnetic material component, wherein said material exhibits both magnetic effects and phase change effects, and is usable for optical media, phase change random access memory (PCRAM) devices, magnetic random access memory (MRAM) devices, solid state memory devices, sensor devices, logical devices, cognitive devices, artificial neuron network, three level device, control device, SOC (system on chip) device, and semiconductors.

This invention relates to a novel material, in particular, a novel phasechange magnetic material and methods of making the same. The inventionalso relates to the uses of the material in optical media, phase changerandom access memory (PCRAM) devices, magnetic random access memory(MRAM) devices, solid state memory devices, sensor devices, logicaldevices, cognitive devices, artificial neuron network, three leveldevice, control device, SOC (system on chip) device, and semiconductors.

BACKGROUND OF THE INVENTION

Over the last three decades, materials for rewritable media have beenreceiving an increasing amount of interest in the scientific communityand the industry. Since the discovery of chalcogenide film materials in1968, materials have developed into a complex technology which find usesin many important applications, including electrical write and erasenon-volatile memory devices, cognitive semiconductors, and rewritableoptical discs.

Recent research efforts have been focussed on the development ofnon-volatile phase change random access memory and rewritable discs withhigh storage capacities and fast read-write speeds. Examples of suchrewritable media that are now widely in use include rewritable compactdiscs (CD-RW), rewritable digital video discs (DVD-RAM, DVD-RW, DVD+RW)and rewritable blue laser optical disc (Blu-ray, HD-DVD).

Phase change media utilise phase change materials as recording media.The media is thermally written and optically read. Data is written anderased by inducing a change in phase of the material between crystallinephase and the amorphous phase. A laser beam is typically used to heatthe material to bring about a change of phase. As each phase isassociated with a different level of light reflectivity, namely, thecrystalline phase is highly reflective, and the amorphous phase is lowlyreflective, both lowly reflective mark and highly reflective backgroundspots can be formed on the material to represent computer-readable databits.

The use of rewritable material for optical discs was first reported in1971 in which the recording media comprised chalcogenide phase-changecomposite material (Feinleib et al., Appl. Phys. Lett. Vol. 18 (1971)pg. 254). Since then, many attempts have been made to provide newmaterials for rewritable media in response to the increase in computerdata size and the corresponding increase in the demand for largerstorage capacity and faster read-write speeds.

For example, U.S. Pat. No. 5,709,978 discloses a phase change recordingfilm for use in double sided optical discs in which the recordingmaterial comprises a phase change component such as Sb—Te—Ge and atleast one lanthanide element and a transition metal. A high meltingpoint component is precipitated in the recording film to coexist with aphase change component to prevent the recording film from flowing andsegregating during recording and erasing.

Another type of rewritable media that is widely in use ismagneto-optical (MO) media (used for example in Mini Discs). MO mediaoperates based on both magnetic and optical storage device principles:writing is carried out magnetically after thermal treatment, and readingis carried out optically. Typically, a focussed laser beam is appliedonto one side of the media in order to heat the MO material to its Curiepoint or compensation temperature, and thus render it susceptible to amagnetic field. A magnetic head positioned on the opposite side of thedisc is then operated to record digital data onto the disk by alteringthe magneto-optical polarity of the heated area.

U.S. Pat. No. 6,132,524 discloses an example of a semiconductormagneto-optical material. The material comprises a semiconductor such asMsAs:GaAs in which fine magnetic particles are dispersed. The materialexhibits magneto-optical effects at room temperature and can be used forsignal processing and the fabrication of optical isolators andintegrated circuits.

Composites comprising two or more kinds of material components and theiruse in recording media have been disclosed in U.S. Pat. No. 5,709,978.In carrying out the synthesis of the composites, material components ofthe composites are either combined and prepared from a simple mixture,or one material component is precipitated in the other materialcomponent. Such composites exhibit either magnetic or phase changeproperties individually, but is incapable of exhibiting both magneticand phase change properties simultaneously.

Several studies into materials for optical discs have been carried out.In a study of the erasing process in optical rewritable discs, Shi etal. discloses the use of phase change material Ge₂Sb₂Te₅ in opticalrewritable discs and the dynamic crystallisation behaviour in relationto the erasure of data on such discs (Jpn. J. Appl. Phys. Vol. 42, Part1, No. 2B, pp 841-847, 2003).

In another study, Sato et al. discloses a GaN-based ferromagneticdiluted magnetic semiconductor for semiconductor devices (Jpn. J. Appl.Phys. Vol. 40, Part 2, No. 5B, pp. L485-L487, 2001). In yet anotherstudy, Sun et al. (Appl. Phys. Lett. Vol. 82 No. 12 pp, 1902-1904,2003.) discloses the use of FePt magnetic films sputtered on Cu.

Despite the developments that have taken place, limitations in currentmaterials still exist. For example, the capacity and recording speed ofrewritable optical media are presently limited by the laser diffractionlimit and the crystallisation speed of the recording material.Therefore, continuing efforts are needed to provide new materials havingnew characteristics.

Accordingly, it is an object of the present invention to provide newmaterials that, for example, give rise to improved performance.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda phase change magnetic composite material which comprises a phasechange material component, and a ferromagnetic material component. Thismaterial has a crystalline phase associated therewith a first magneticproperty and a first phase change material property. In addition, thismaterial has an amorphous phase associated therewith a second magneticproperty and a second phase change material property. The material ofthe invention has unique electrical, magnetic, thermal, crystallizationand optical properties at different phases, such as fully crystallinestates, amorphous, and partial crystalline phases. The material exhibitsboth magnetic effects and phase change effects and can be used in a widerange of applications. Examples of applications in which the materialmay be used include, but are not restricted to, optical media, phasechange random access memory (PCRAM) devices, magnetic random accessmemory (MRAM) devices, solid state memory devices, sensor devices,logical devices, cognitive devices, artificial neuron network, threelevel devices, control devices, SOC devices and semiconductors.

According to another aspect of the invention, there is provided anoptical recording medium for recording information, said mediumcomprising the phase change magnetic material of the invention. Theinvented material has different electrical, magnetic, and opticalproperties at different phase states, such as crystalline states,amorphous, and partial crystalline. The invention further relates to theuses of the phase change magnetic material in devices such as solidstate memory devices, semiconductors, logical devices, magnetic randomaccess memory, artificial neuron network, and phase change random accessmemory devices.

These aspects and other aspects of the invention will be more fullyunderstood in view of the following description, drawings andnon-limiting examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the synthesis of phase changemagnetic material according to one embodiment of the present invention.

FIG. 2 a shows graphical data characterising the magnetic properties ofa conventional phase change material Ge₂Sb₂Te₅; as can be seen from thefigure, the material exhibits antimagnetic properties.

FIG. 2 b shows graphical data characterising the magnetic properties ofa phase change magnetic material, Fe_(4.4)Ge_(14.8)Sb_(34.2)Te_(46.6)according to one embodiment of the invention. Coercivity value H_(c) of38 Oersteds is observed at zero magnetization.

FIG. 2 c shows graphical data characterising the magnetic properties ofphase change material of GeTe.

FIG. 2 d show magnetic properties of phase change magnetic material ofFe_(4.6)Pt_(7.3)Ge_(59.5)Te_(28.6) according to the present invention.

As shown in FIGS. 2( a-d), conventional phase change materials exhibitsantimagnetic property while phase change magnetic material according tothe present invention shows magnetic property.

FIGS. 3 a and 3 b shows graphical data characterising the magneticproperties of the Co_(6.3) Ge_(31.1) Sb_(27.1) Te_(35.5) in theamorphous and crystalline state.

FIG. 4 is a microscope photograph of the material according to theinvention at amorphous and crystalline phases as induced by a pulselaser. The photograph indicates that the phase change magnetic materialhas different optical properties in the amorphous and the crystallinephases, similar to phase change materials. The experiment also showedthat between crystal and amorphous there are partial crystalline statesmeaning the crystalline fraction x is in the range, 0<x<1.

FIG. 5 shows a table of data comparing the electrical resistivity ofconventional phase change materials and the phase change magneticmaterial of the invention at amorphous and crystalline states. The datashows that phase change magnetic material according to the inventionhave similar electrical properties to phase change materials.

FIGS. 6 a and 6 b show XRD profiles characterising the crystal structureof 2 different phase change magnetic materials, namely,Fe_(4.4)Ge_(14.8)Sb_(34.2)Te_(46.6) andFe_(4.6)Pt_(7.3)Ge_(59.5)Te_(28.6).

FIGS. 7 a and 7 b show schematic diagrams of a laser ablation system anda sputtering system, respectively, which can be used for synthesisingthe phase change magnetic material of the invention.

DETAILED DESCRIPTION

The invention is based on the finding that phase change materials andmagnetic materials can be used to form a homogeneous composite materialthat exhibits both phase change effects as well as magnetic effects. Inthe context of the present invention, a material is said to exhibitphase change effects if it shows changes in its physical properties whenit undergoes a phase change. Examples of these physical propertiesinclude resistivity, absorption at different wavelength, opticalconstants, dispersion relation, dielectric constants, density, thermalconductivity, thermal diffusion coefficient, specific heat, activeenergy, lattice constant, crystallization temperature, glasstemperature. Likewise, a material is said to exhibit magnetic effects ifit is under a magnetic field.

Without wishing to be bound by theory, the inventors presently believethat under appropriate growth conditions, phase change components andmagnetic components can be combined such that the crystal structure ofthe resulting phase change magnetic material is altered: some of theatoms of the phase change material is replaced by the atoms of magneticmaterial in the crystal structure, so a new unit cell having a uniquecrystal structure is formed. In other words, atoms of magnetic materialare made to replace the positions of some atoms of phase changematerial, without destroying crystal structure of phase change material.In this manner, phase change magnetic composite materials are able toexhibit both phase change effects due to similar crystal structure withphase change material, and magnetic effects due to magnetic atomsexisting in the crystal structure.

One advantage that is provided by the material of the invention is thateach phase of the material is coupled to a unique set of phase changeproperties and magnetic properties. This means that when the materialundergoes phase change from crystalline phase to amorphous phase, forinstance, the material exhibits a corresponding change in both its phasechange properties (e.g. optical reflectance, optical constants) and itsmagnetic properties (e.g. field strength). The benefit of dual propertychange can be harnessed for a wide variety of applications, such assensing, data storage, logical, cognitive, control, SOC (system on chip)and semiconductor applications. For recording applications for instance,this property enables the readout signal from the contribution of boththe optical reflectance change, polarization, frequency and magneticchange to be detected at the same time and at the same point, therebyincreasing the recording density and data transfer rate in recordingmedia utilising the material of the invention. In sensing applications,this property enables sensing measurements to be highly accurate forelectric, thermal, optical, magnetic, magneto-optical, thermal-electric,electric-optical and their combination.

Phase change properties exhibited by the phase change magnetic material(hereinafter referred to as “PCM material”) of the present inventioninclude the properties of high electrical resistivity, low thermalconductivity, and low light reflectivity in the amorphous phase, and lowelectrical resistivity, high thermal conductivity and high lightreflectivity in the crystalline phase. The physical parameters such asresistivity, reflectivity, absorption, optical constants, refractionindex and absorption coefficient, dielectric constants, density, thermalconductivity, thermal diffusion coefficient, specific heat, activeenergy, and so on are different at partial crystalline states rangingfrom those at the amorphous state to those at the crystalline state.These properties are similar to those exhibited by known phase changematerials and are thus presently known as phase change effects.

Magnetic properties (hereinafter used interchangeably with the term“magnetic effects”) exhibited by the material include havingparamagnetic properties in the amorphous (disordered) phase and magneticproperties in the crystalline (ordered) phase. Magnetic effects alsoinclude changes of magnetic properties such as the saturationmagnetization Ms, coercive field Hc, anisotropy field H_(k), uniaxialanisotropy constant Ku, squareness, remanence magnetization Mr,saturation induction Bs, Curie temperature Tc, compensation temperatureand so on. These properties are similar to those exhibited by magneticmaterials and are thus presently known as magnetic effects.

The phase change magnetic composite material of the invention comprisestwo main components, namely a phase change component and a magneticcomponent.

The phase change component comprises any type of phase change material.It is preferable in some embodiments that the phase change materialexhibits phase change (i.e. it may melt) at a temperature above standardroom temperature (i.e. 25° Celsius), or more preferably, at an elevatedtemperature of more than a hundred, or more than several hundred degreesCelsius. The elevated temperature can be brought about by any suitablefocussed laser beam or any electric current or heating device. Forrecording purposes, the phase change material preferably changes fromthe crystalline phase to the amorphous phase upon heating and subsequentcooling, and does not regain the crystalline conformation. In thismanner, the amorphous marks in combination with the crystalline areasmay be used to represent data. It is possible to also use phase changematerials in which phase change occurs at temperatures higher than thetemperatures that can be provided by standard laser equipment. If used,such materials require higher operating power in order to induce thephase change. On the other hand, phase change materials such as paraffinwax and polyimides (e.g. polymeric organic substances) which are usedfor thermal insulation of buildings, for example, are not considered tobe suitable for use in the invention due to the relatively low phasechange temperature.

In one embodiment, the phase change component is selected from anelement from any of the Groups IIIB, IVB, VB and VIB of the PeriodicTable. In some embodiments, preferred elements are selected from, butare not restricted to, the chalcogen elements Te, S, Po and Se, as wellas other elements such as P, As, Sb, Bi, Ge, Sn, Pb, Ga, In, and Ti.

In a presently preferred embodiment, the phase change componentcomprises a chalcogenide alloy. Examples of suitable secondary, ternaryand quaternary chalcogenide alloy systems include, but are not limitedto, Ge—Te, Sb—Te, Ge—Sb, Sn—Te, Sb—Se, In—Se, Ge—Sb—Te, Pt—Ge—Te,In—Sb—Te, As—Sb—Te, As—Ge—Te, Se—Sb—Te, Sn—Te—Se, Ge—Te—Sn, Sb—Se—Bi,Ga—Te—Se, In—Se—Ti, Ge—Te—Ti, Ge—Te—Sn—O, Ge—Te—Sn—Au, Ge—Te—Sn—Pd,Ag—In—Sb—Te and mixtures thereof. Presently preferred quaternary systemsinclude Ge—Sb—Te—X and In—Sb—Te—X wherein X is a transition metal suchas Au, Pd, Ir, Ru, Re, Mo, Ta, Zr and La. Each element in thesepresently preferred alloy systems can be present in any suitable atomicpercentage. Some examples of presently preferred alloy compositionsinclude, but are not limited to, Ge₂Sb₂Te₅, GeSb₂Te₄, GeSb₃Te₄,GeSb₄Te₇, In₃SbTe₂, Ag₅In₅Sb₆₀Te₃₀, Sb₂Te₃, Sb₇₀Te₃₀, GeTe, GeSb,Sb₂Se₃, Sb₂Te₃—GeTe, for instance.

The second component present in the phase change magnetic material ofthe invention is a ferromagnetic component. The term “ferromagneticcomponent” refers to materials having a large and positivesusceptibility to an external magnetic field. Typically, such materialshave unpaired electrons whose spins results in a net magnetic moment tobe generated in each atom of the ferromagnetic material. The electronspins of the atoms are aligned in microscopic regions known as domains.In these domains, large numbers of atoms (typically about 10¹² to 10¹⁵)are aligned in parallel so that the magnetic force within the domain isstrong. When a ferromagnetic material is in the unmagnetized state, thedomains are nearly randomly organized and the net magnetic field for thepart as a whole is zero. When the ferromagnetic material is broughtwithin the influence of a magnetic field, the domains become alignedwith the magnetic field, thereby producing a strong magnetic fieldwithin that part of the material.

In one embodiment, the ferromagnetic component that is used in thepresent invention is selected from, but not limited to, the elementsiron, nickel, and cobalt. Further examples include ferromagnetic alloyscomprising at least one ferromagnetic component, such as such iron,nickel, and cobalt. Examples of ferromagnetic alloys comprising at leastone ferromagnetic component includes FePt, CoPt, PdCo, TbFeCo, GdFeCo,CoCrPtB, and CoCrPtTa, to name only a few.

When the material of the invention is used in a conventional recordingmedium such as compact discs, digital video disc, and magnetic mediasystems, the proportion of each of the phase change component and themagnetic component is selected such that the resulting materialpossesses characteristics or exhibits properties that are desirable inconventional phase change media, conventional magnetic media and as wellas conventional magneto-optical media, so that the medium is able tofunction according to the requirements of standard reading and recordingequipment. To achieve this purpose, the components of the phase changemagnetic material can be selected such that the composite materialexhibits at least one physical state selected from a crystalline state,an amorphous state and a partial crystalline state. The components ofthe phase change magnetic material can also be selected such that thecomposite material exhibits different electrical, magnetic, thermal,crystallization, and optical properties at each of said at least onephysical state.

Desirable characteristics in a phase change optical media includesdifferent refractive indexes for the crystalline and amorphous phases(for optical contrast), low melting point (for low laser power), highcrystallization speed and good amorphous stability. Desirablecharacteristics in a magnetic media includes perpendicular magneticanisotropy (for facilitating perpendicular magnetic recording), smallgrain size, high perpendicular coercivity, high perpendicularanisotropy, high squareness, proper saturation magnetization. Desirablecharacteristics in a magneto-optical media includes an amorphousstructure (for smooth surface and domain's boundaries to decreasesystem's noise), suitable Curie temperature (for media stability and lowlaser power), rapid drop of coercivity near the Curie temperature (forsharp recording threshold), perpendicular magnetic anisotropy, chemicalstability (for constant material's properties under repeatedheating-cooling) and high coercivity at room temperature (for mediastability, accidental data loss prevention). Accordingly, in oneembodiment, the components of the material are selected to achieve atleast one of the above properties.

In one embodiment, the phase change component and ferromagneticcomponent are present in a proportion such that the resulting phasechange material has a crystalline phase associated therewith a firstmagnetic property and a first phase change property, and an amorphousphase associated therewith a second magnetic property and a second phasechange property. The proportion of each component present in thematerial should enable the second set of magnetic and phase changeproperties to be distinct and different from the first set properties,thereby enabling these properties to be used for representing recordedinformation on the material.

In some embodiments, the resistivity p of said material is generally inthe range of 1×10⁻³ Ωcm <ρ<1×10³ Ωcm, or 0.1 Ωcm <ρ<10 Ωcm at amorphousstate and in the range of 1×10⁻⁴ Ωcm <ρ<1×10⁻¹ Ωcm, or 1×10⁻⁷ Ωcm<ρ<1×10⁻² Ωcm at crystalline state. The resistivity difference of saidmaterial between the amorphous phase and the crystalline phase by atleast about a factor of 2 to 10⁶. In other preferred embodiments, thecoercivity of the material in the crystalline phase is at least about 1Oersted, or in some cases, at least about 40 Oersteds.

In a further embodiment, the phase change magnetic material has acrystal structure that is at least substantially similar to the phasechange material component. In this embodiment, the atoms of magneticmaterials replace the position of some atoms of phase change materialswithout destroying crystal structure of phase change materials. As theatoms of magnetic elements or materials replace the positions of someatoms of phase change material to form a new unit cell with uniquecrystal structure under appropriate growth conditions and thereplacement is in a certain range of replacement, these materialsexhibit both phase change effect and magnetic effect.

In a further embodiment, the phase change magnetic material has acomposition of formula (I):

A_(x)B_(y)

wherein

A denotes the ferromagnetic component;

B denotes the phase change component;

x denotes the total atomic percentage of A, wherein 1%≦x≦50%, and ydenotes the total atomic percentage of B, wherein 50%≦y≦99%.

In one presently preferred embodiment, the phase change magneticmaterial as defined in formula (I) has a ferromagnetic component Aselected from any of the elements Co, Fe Ni and the alloy FePt, and aphase change component B selected from Sb, Te, GeTe, Sb₂Te₃, GeSb,Sb₇₀Te₃₀, InSbTe, Ag—In—Sb—Te and Ge—Sb—Te. The chemical formula ofcomposite materials having the formula (I) may be selected from one ofthe following simplified chemical formula: Fe(Sb₂Te₃), Co(Sb₂Te₃),Ni(Sb₂Te₃), FeGeSb, CoGeSb, NiGeSb, Fe(Sb₇₀Te₃₀), Co(Sb₇₀Te₃₀),Ni(Sb₇₀Te₃₀), FeInSbTe, CoInSbTe, and NiInSbTe. Illustrative examplesinclude, but are not limited to, Co_(6.3) Ge_(31.1) Sb_(27.1)Te_(35.5),Co_(3.6) Ge_(20.8) Sb_(30.5)Te_(44.9), Co_(2.8) Ge_(17.9)Sb_(31.9)Te_(47.1), Co_(6.1) Ge_(14.3) Sb₃₃Te_(46.5), Co_(3.0) Ge_(18.5)Sb_(30.1) Te_(48.2), Co_(5.0) Ge_(16.9) Sb_(31.6)Te_(46.5), Co_(1.5)Ge_(17.3) Sb_(32.9)Te_(48.3), Co_(5.4) Ge_(17.2) Sb_(30.5)Te_(46.9),Co_(2.0) Ge_(17.7) Sb_(32.5)Te_(47.8), Co_(5.8) Ge_(17.1)Sb_(32.3)Te_(44.8), Co_(4.6) Ge_(14.9) Sb_(33.4)Te_(47.1), Co_(10.1)Ge_(14.4)Sb_(34.6)Te_(40.9), Co_(26.1) Ge_(17.2) Sb_(22.1)Te_(34.6),Co_(5.6)Ge_(15.8)Sb_(33.6)Te₄₅, Fe_(20.2) Ge_(21.5) Sb_(16.9) Te_(41.4),Fe_(9.2) Ge_(16.3) Sb_(27.4) Te_(47.2), Fe_(4.7) Ge_(18.5) Sb_(28.1)Te_(48.6), Fe_(4.4) Ge_(14.8) Sb_(34.2) Te_(46.6), Fe_(11.1) Ge₁₆Sb_(25.9) Te_(47.1), Fe_(1.0) Ge_(15.7) Sb_(35.2) Te_(48.2), Fe_(7.2)Ge_(14.7) Sb_(32.9) Te_(45.2), Fe_(28.2) Pt_(32.4) Ge_(30.0) Te_(9.3),Fe_(4.1) Pt_(4.2) Ge_(64.5) Te_(27.1), Fe_(2.1) Pt_(5.5) Ge_(63.9)Te_(28.4), Fe_(1.1) Pt_(2.7) Ge_(64.3) Te_(31.9), Fe_(4.6) Pt_(7.3)Ge_(59.5) Te_(28.6), Fe_(5.0) Pt_(6.8) Ge_(59.6) Te_(28.6), Fe_(1.1)Pt_(1.1) Ge_(50.4) Te_(31.1), Fe_(4.8) Pt_(4.6) Ge_(58.2) Te_(32.4), andFe_(1.2) Pt_(2.5) Ge_(54.2) Te_(41.9),Fe_(1.0)Pt_(2.0)Ge_(62.1)Te_(34.9).

In a further embodiment, the phase change magnetic material has acomposition of formula (II):

A_(x)B_(y)C_(z)

wherein

A denotes a ferromagnetic component;

B denotes a phase change component;

C denotes a manganese compound component;

x denotes the total atomic percentage of A, wherein 1%≦x≦40%, y denotesthe total atomic percentage of B, wherein 40%≦y≦98%, and z denotes thetotal atomic percentage of C, wherein 1%≦y≦20%.

In one presently preferred embodiment, the phase change magneticmaterial as defined in formula (II) has a ferromagnetic component Aselected from any of the elements Co, Fe Ni and the alloy Fe—Pt, and aphase change component B selected from Sb, Te, GeTe, Sb₂Te₃, GeSb,Sb₇₀Te₃₀, InSbTe, Ag—In—Sb—Te and Ge—Sb—Te. The third component C isselected from MnAs, MnGa, MnSb, and MnAl. Components A and B ofpresently preferred composite materials having the formula (II) arepresently preferably combined to form one of the following compounds:Fe(Sb₂Te₃), Co(Sb₂Te₃), Ni(Sb₂Te₃), FeGeSb, CoGeSb, NiGeSb,Fe(Sb₇₀Te₃₀), Co(Sb₇₀Te₃₀), Ni(Sb₇₀Te₃₀), FeInSbTe, CoInSbTe, andNiInSbTe. Illustrative examples include, but are not limited to,Co_(6.3) Ge_(31.1) Sb_(27.1)Te_(35.5), Co_(3.6) Ge_(20.8)Sb_(30.5)Te_(44.9), Co_(2.8) Ge_(17.9) Sb_(31.9)Te_(47.1), Co_(6.1)Ge_(14.3) Sb₃₃Te_(46.5), Co_(3.0) Ge_(18.5) Sb_(30.1) Te_(48.2),Co_(5.0) Ge_(16.9) Sb_(31.6)Te_(46.5), Co_(1.5) Ge_(17.3)Sb_(32.9)Te_(48.3), Co_(5.4) Ge_(17.2) Sb_(30.5)Te_(46.9), Co_(2.0)Ge_(17.7) Sb_(32.5)Te_(47.8), Co_(5.8) Ge_(17.1) Sb_(32.3)Te_(44.8),Co_(4.6) Ge_(14.9) Sb_(33.4)Te_(47.1), Co_(10.1)Ge_(14.4)Sb_(34.6)Te_(40.9), Co_(26.1) Ge_(17.2) Sb_(22.1)Te_(34.6),Co_(5.6)Ge_(15.8)Sb_(33.6)Te₄₅, Fe_(20.2) Ge_(21.5) Sb_(16.9) Te_(41.4),Fe_(9.2) Ge_(16.3) Sb_(27.4) Te_(47.2), Fe_(4.7) Ge_(18.5) Sb_(28.1)Te_(48.6), Fe_(4.4) Ge_(14.8) Sb_(34.2) Te_(46.6), Fe_(11.1) Ge₁₆Sb_(25.9) Te_(47.1), Fe_(1.0) Ge_(15.7) Sb_(35.2) Te_(48.2), Fe_(7.2)Ge_(14.7) Sb_(32.9) Te_(45.2), Fe_(28.2) Pt_(32.4) Ge_(30.0) Te_(9.3),Fe_(4.1) Pt_(4.2) Ge_(64.5) Te_(27.1), Fe_(2.1) Pt_(5.5) Ge_(63.9)Te_(28.4), Fe_(1.1) Pt_(2.7) Ge_(64.3) Te_(31.9), Fe_(4.6) Pt_(7.3)Ge_(59.5) Te_(28.6), Fe_(5.0) Pt_(6.8) Ge_(59.6) Te_(28.6), Fe_(1.1)Pt_(1.1) Ge_(50.4) Te_(31.1), Fe_(4.8) Pt_(4.6) Ge_(58.2) Te_(32.4),Fe_(1.2) Pt_(2.5) Ge_(54.2) Te_(41.9), andFe_(1.0)Pt_(2.0)Ge_(62.1)Te_(34.9).

It would be understood by a person skilled in the art that the phasechange magnetic material of the invention can be used in conjunctionwith any suitable type of secondary material known in the art which aidsin the optical media, phase change random access memory (PCRAM) devices,magnetic random access memory (MRAM) devices, solid state memorydevices, sensor devices, logical devices, cognitive devices, artificialneuron network, and semiconductors of the material of the invention.Secondary materials include dyes for improving reflectivity, sacrificialcoatings for preventing moisture degradation, for example.

In order for both phase change effects and magnetic effects to beexhibited in the material, the phase change component and theferromagnetic component may be present in the material according to asuitable ratio which allows the atoms of the magnetic material toreplace the atoms of the phase change material without resulting in anysubstantial change in the crystal structure of the phase change materialMany methods are suitable for the synthesis of the phase change magneticmaterial of the invention. Examples of methods which enable ahomogeneous composite material to be formed and can thus be used herein,include laser ablation, sputtering, ion plating, chemical vapordeposition (CVD), plasma enhanced chemical vapor, metal organic chemicalvapor deposition, spin coating, molecular beam epitaxy (MBE), top-seededsolution growth, thermal pressing, vacuum melting, and conventionalcrystal growth.

In one embodiment, the material of the invention is synthesized by laserablation or by laser synthesis. Preferably, the material is synthesisedvia laser synthesis. In the context of the present invention, the methodof synthesis involving dual-beam laser ablation of different targets forsynthesizing new materials within the overlapping plasma area isincluded in the term “laser synthesis”. Laser synthesis is carried outby laser pulses from an excimer laser used to heat precursor componentmaterials that are mounted onto rotating mounts. By positioning themounts such that the plumes emitted from the precursors overlap at leastpartially, a substrate can be positioned within this overlapping regionso that a homogeneous film can be formed thereon. This procedure isdescribed, for example, by Song et al. (Appl. Phys. A. Vol. 79 p1349-1352, 2004).

In another aspect, the invention relates to an optical recording mediumfor recording information, comprising a phase change magnetic material,said material comprising a phase change component and a ferromagneticcomponent, wherein said material exhibits both magnetic effect and phasechange effect. The design of an optical disc as such and method ofmanufacturing an optical disc are known to the person of average skillin the art and described for example, in U.S. Pat. No. 6,469,977. Actualimplementations of such an optical disc include CD-RW, DVD-RAM, DVD-RW,DVD+RW, Blu-ray, HD-DVD. Next generation products of optical discsincluding discs with holography recording, near field optical recording,multi layer optical recording and multi-level recording have been thesubject of intense research in recent years. Other uses of the phasechange magnetic material according to the invention include the use inphase change random access memory (PCRAM) devices, magnetic randomaccess memory (MRAM) devices, solid state memory devices, sensordevices, logical devices, cognitive devices, three level device, controldevice, and semiconductors.

In actual use, an information recording medium which has a recordinglayer comprising the material of the invention is provided with thephase change magnetic material in either crystalline phase or inamorphous phase. During recording procedure, a laser selectively heatsareas of a recording track present in the optical disc above the phasechange magnetic material's melting point or crystallization temperature.The material is melted and subsequently ‘frozen’ by quickly cooling thelayer or is crystallized. The reflectance of the amorphous areas is muchdifferent with that of the crystalline areas which, during readout,gives rise to a signal similar to that produced from the pits and landsof a ROM type disc. The change in optical reflectance can be used torepresent stored data on the recording medium. A new overwriting signalcan be recorded by erasing an existing recorded signal, using bymodulating the laser output of the recording laser beam. Duringoverwrite, some amorphous areas along the track are returned to thecrystalline phase by annealing below the melting point with the use of afocussed laser beam, the material is locally heated to a temperature ofapproximately between the melting point and crystallisation temperaturefor a certain retention time in order to carry out re-crystallisation.Similarly, some crystalline areas are converted to the amorphous phaseby heating above the melting point, then quenching as described above.This process can be repeated several thousand times per disc. Forrewritable optical media, the background is in some cases preferablycrystalline. The media using phase change magnetic material of theinvention can also be made to be written once. For write once media orso-called “recordable media”, the background of the disc can be eithercrystalline or amorphous.

At the same time, when the material is reversibly changed betweenamorphous and crystalline states, the magnetic properties of thematerial of the invention is correspondingly changed because of thestructural change. Thus, this structural change can be detected bymeasuring the readout signal associated with the change in magneticproperties. Finally, the readout signal from the contribution of boththe optical reflectance change and magnetic change is detected at thesame time and at the same point. The recording density and data transferrate will be increased. For conventional phase change media, only theoptical reflectance change from the material can be detected. For thematerial of the invention, both the optical reflectance change andmagnetic change can be detected at the same time and at the same point(location). The recording density and data transfer rate will beincreased.

In utilising the magnetic properties of the material, conventionalmethods used for reading and writing magneto-optical discs can becarried out. For example, during reading, a laser projects a beam on thedisk and the changes in the polarisation of reflected light isinterpreted as binary data. The reflected light varies according to themagnetic data stored on the disc. The changes in light polarizationoccur due to the presence of a magnetic field on the surface of the disk(the Kerr effect). If a beam of polarized light is shone on the surface,the light polarization of the reflected beam will change slightly(typically less than 1°), provided it is reflected from a magnetizedsurface. If the magnetization is reversed, the change in polarization(the Kerr angle) is reversed as well. The magnetized areas—pits—cannotbe seen in regular light, but only in polarized light. The change isdirection of magnetization can be associated with numbers 0 or 1, thusallowing the storage of binary data. During recording, the light becomesstronger so it can heat the material up to the Curie point orcompensation temperature in a single spot. This allows an electromagnetpositioned on the opposite site of the disc to change the local magneticpolarization, and the polarization is retained when temperature drops.This fact that the material's coercivity drops at higher temperaturesallows thermally-assisted magnetic recording to be carried out withrelatively weak magnetic fields.

At the same time, when light polarization of the material changesbecause of the magnetization reversal, the structure the inventedmaterial is reversibly changed between amorphous and crystalline states,this change can be detected and a reflectance change is observed fromthe readout signal because of structural change. Finally, the combinedreadout signal from the contribution of both the light polarizationchange and optical reflectance change is detected at the same time andat the same point/location. The recording density and data transfer ratewill be increased as a result. For conventional magneto-optical medium,only the light polarization change by magnetic reverse can be detected.For the material of the invention, both the light polarization changeand optical reflectance change will be detected at the same time and atthe same point. The recording density and data transfer rate isconsequently increased.

EXAMPLE 1 Laser Synthesis Synthesis Procedure

The schematic diagram of our laser synthesis system is shown infollowing FIG. 7( a). The synthesis was carried out in chamber 8. A KrFexcimer laser beam from the laser 10 was split into two beams viasplitter 12, and were focused onto two rotating targets 14 with twofocus lenses 16, 18 and with the aid of two reflectors 30. Twooverlapping plumes were produced on substrate 20, respectively. Thelaser fluence on each target is between 0.5 and 6 J/cm². The targetswere mounted at 45° with respect to the laser beams. Facing the targetsat a distance of 2 to 8 cm, substrate 20 was mounted on a two-inchstainless steel holder 22 by silver paste. The two mirrors is to reflectthe splitted laser onto the focussing lens. A background pressure of2×10⁻⁶ Torr was achieved with a turbomolecular pump (not indicated). Thegrowth temperature was between room temperature and 900° C. Thesynthesized materials were typically grown for 12000 pulses at arepetition rate of 10 Hz. After laser synthesis, the materials werecooled to room temperature.

In the context of the present invention, the method of synthesisinvolving dual-beam laser ablation of different targets for synthesizingnew materials within the overlapping plasma area is termed “lasersynthesis”. In this method, the components including atoms, molecules,electrons, ions and clusters for material synthesis are highly energeticevaporants generated by laser ablation. The use of short laser pulsesfor ablation is more likely to achieve congruent ablation to preservestoichiometry during mass transfer from target to substrate, which makescomposition of new material easily controlled. Since laser interactionwith gas-phase species is relative weak, many kinds of reactive gasescan be input for material synthesis. It is flexible in tuningsynthesized elements and composition by varying target, laser fluenceand input gas as well as substrate position within the overlappingplasma area. A preferred single crystal substrate can be chosen to leadto crystal growth of new materials. It can also heat the substrate tohigh temperature to provide an appropriate environment for new materialsynthesis. The method is inexpensive, simple and fast to synthesize newmaterials.

According to the above experimental conditions, one target was selectedfrom Fe, Co, FePt and another target was selected from Ge₂Sb₂Te₅ andGeTe. Three groups of phase change magnetic materials were synthesized.They comprised Co—Ge—Sb—Te, Fe—Ge—Sb—Te and Fe—Pt—Ge—Te systems. Thecomposition of the materials produced were analysed by X-rayphotoelectron spectroscopy (XPS). The crystal structures were analysizedby XRD. The magnetic, electrical and optical properties were all tested.

As shown in FIGS. 2 a to 2 d, a conventional phase change material suchas Ge₂Sb₂Te₅ and GeTe exhibits antimagnetic property while phase changemagnetic materials of the invention show magnetic property. Incomparison, as shown in FIGS. 3 a and 3 b, the phase change magneticmaterial at crystalline state exhibits stronger magnetic property thanthe phase change magnetic material at amorphous state. This indicatesthat magnetic properties of phase change magnetic material vary with astate change of phase change magnetic material.

FIG. 4 is a microscope photo showing contrast change between amorphousand crystalline phases induced by a pulse laser for the phase changemagnetic material according to one embodiment of the present invention.It indicates that the phase change magnetic material has differentoptical properties between amorphous and crystalline phases, which issimilar with phase change material.

FIG. 5 shows a table of data comparing the electrical resistivity ofconventional phase change material and the phase change magneticmaterial according to one embodiment of the present invention atamorphous and crystalline states. It indicates both the phase changematerial and the phase change magnetic material exhibit relatively largedifferences in electric properties between amorphous state andcrystalline state. This means that phase change magnetic material has asimilar electric property with conventional phase change material.

In summary, phase change magnetic materials of the invention not onlydisplay characteristics of conventional phase change materials, but alsomagnetic properties and characteristics of magnetic semiconductormaterials.

FIG. 6 a shows the XRD profile characterising the crystal structure of asample Fe_(4.4)Ge_(14.8)Sb_(34.2)Te_(46.6). As can be seen from thefigure, the material exhibited crystalline peaks, thus confirming theexistence of a crystalline phase for a Fe—Ge—Sb—Te system synthesised at300° C. An analysis of the peak position identified that the crystalstructure of the synthesised Fe_(4.4)Ge_(14.8)Sb_(34.2)Te_(46.6) to besimilar to the crystal structure of Ge₂Sb₂Te₅.

The second sample comprised a Fe—Pt—Ge—Te system that was synthesisedaccording to the synthesis procedure described above. XPS analysisrevealed the composition of the synthesised material to beFe_(4.6)Pt_(7.3)Ge_(59.5)Te_(28.6). FIG. 6 b shows the XRD profilecharacterising the crystal structure of the sample. As can be seen fromthe XRD profile, the material exhibited crystalline peaks, thusconfirming the existence of a crystalline phase for a Fe—Pt—Ge—Te systemsynthesised at 300° C. An analysis of the peak position identified thatthe crystal structure of the synthesisedFe_(4.6)Pt_(7.3)Ge_(59.5)Te_(28.6) to be similar to the crystalstructure of GeTe.

Based on the experimental results shown in FIGS. 6 a to 6 b, it can beconcluded that phase change magnetic materials have similar crystalstructures as phase change materials, or the phase change materialcomponent used to synthesise it. One possible explanation for thisproperty is that the atoms of magnetic materials have replaced the atomsof phase change materials in the unit cell of the phase change material,without destroying/disrupting its crystal structure. Therefore, the newmaterial exhibits not only phase change effects due to its similarcrystal structure as phase change material, but also magnetic effectscaused by the presence of magnetic atoms in the crystal structure.

EXAMPLE 2 Synthesis by Sputtering Synthesis Procedure

Sputtering method can be employed to synthesize the invented material.In our sputtering system supplied by Leybold Vacuum and schematicallyillustrated in FIG. 7( b), two DC sputtering cathodes and two RFsputtering cathodes are installed and four targets, 2 of which arelabelled DC01 and DC02, and the other are labelled RF02 and RF01, arephysically separated from each other. The positions of cathodes areunder the targets in FIG. 7( b). The rotary substrate lies on awater-cooled rotation table and the substrate holder as placed 50 mmabove the targets. A preshutter 48, which can be controlled to be openor close, is between the targets and substrate holder. The substrate,targets and shutter are placed in a vacuum chamber. Argon gas 50 isintroduced into the chamber at low pressure and used as the sputteringgas. A gas plasma is struck using a power source and the gas becomesionized. The ions are accelerated towards and bombards the targetsurface, the target atoms are broken off from the target and depositedon the substrate surface. The thin film of invented material isfabricated on the substrate by pausing substrate under the aimed targetand opening the shutter during a programmed time controlled by acomputer 60.

1-23. (canceled)
 24. A homogeneous phase change magnetic composite material exhibiting both magnetic effects and phase change effects, comprising: a phase change material component, and a ferromagnetic material component, wherein said phase change magnetic composite material has a single crystalline phase associated therewith a first magnetic property and a first phase change property, wherein atoms of the magnetic material component have replaced atoms of the phase change material component in the unit cell of the phase change material component, without destroying/disrupting its crystal structure, and an amorphous phase associated therewith a second magnetic property and a second phase change property, wherein when the material undergoes phase change from crystalline phase to amorphous phase, the material exhibits a corresponding change in both its phase change properties and its magnetic properties.
 25. The phase change magnetic material of claim 24, wherein said first and said second phase change property each comprises at least one property selected from electrical resistivity, thermal conductivity, light reflectivity, refractive index, absorption coefficient, dielectric constant, and thermal diffusion coefficient.
 26. The phase change magnetic material of claim 24, wherein said first and said second magnetic property each comprises at least one property selected from saturation magnetization, coercive field, anisotropy field, uniaxial anisotropy, squareness, remanence magnetization, saturation induction, Curie temperature and compensation temperature.
 27. The phase change magnetic material of claim 24, wherein said material exhibits at least one physical state selected from a crystalline state, an amorphous state and a partial crystalline state.
 28. The phase change magnetic material of claim 27, wherein said material exhibits different electrical, magnetic, thermal, crystallization, and optical properties at each of said at least one physical state.
 29. The phase change magnetic material of claim 24, wherein said material in the crystalline state has a coercivity of at least about 1 Oersteds.
 30. The phase change magnetic material of claim 24, wherein the resistivity ρ of said material is in the range of 1×10⁻³ Ωcm <ρ<1×10³ Ωcm at amorphous state and in the range of 1×10⁻⁴ Ωcm <ρ<1×10⁻¹ Ωcm at crystalline state, the resistivity difference of said material between the amorphous state and the crystalline state being in the magnitude of 2 to 10⁶.
 31. The phase change magnetic material of claim 24, wherein said phase change material component comprises at least one element selected from Group IIIB, IVB, VB or VIB of the Periodic Table.
 32. The phase change magnetic material of claim 31, wherein the phase change material component is an element selected from the group consisting of Te, S, Se, Po, P, As, Sb, Bi, Ge, Sn, Pb, Ga, In, and Ti.
 33. The phase change magnetic material of claim 31, wherein the phase change component comprises a chalcogenide alloy.
 34. The phase change magnetic material of claim 33, wherein the chalcogenide alloy is selected from the group consisting of the following systems: Ge—Te, Sb—Te, Sn—Te, Sb—Se, In—Se, Ge—Sb—Te, Pt—Ge—Te, In—Sb—Te, As—Sb—Te, As—Ge—Te, Se—Sb—Te, Sn—Te—Se, Ge—Te—Sn, Sb—Se—Bi, Ga—Te—Se, In—Se—Ti, Ge—Te—Ti, Ge—Te—Sn—O, Ge—Te—Sn—Au, Ge—Te—Sn—Pd, Ge—Sb—Te—Se, Ag—In—Sb—Te and mixtures thereof.
 35. The phase change magnetic material of claim 34, wherein the chalcogenide alloy comprises a system having a formula selected from the group consisting of Ge₂Sb₂Te₅, GeSb₂Te₄, GeSb₃Te₄, GeSb₄Te₇, In₃SbTe₂, Ag₅In₅Sb₆₀Te₃₀, Sb₂Se₃, Sb₂Te₃, Sb₇₀Te₃₀, GeTe, GeSb, and Sb₂Te₃—GeTe.
 36. The phase change magnetic material of claim 24, wherein said ferromagnetic material component is selected from the group consisting of Fe, Co, Ni, FePt, CoPt, PdCo, TbFeCo, GdFeCo, CoCrPtB, CoCrPtTa.
 37. The phase change magnetic material of claim 24, wherein said material has a composition of formula (I): A_(x)B_(y) wherein A denotes the ferromagnetic material component; B denotes the, phase change material component; x denotes the total atomic percentage of A, wherein 1%≦x≦50%, and y denotes the total atomic percentage of B, wherein 50%≦y≦99%.
 38. The phase change magnetic material of claim 24, having a composition of formula (II): A_(x)B_(y)C_(Z) wherein A denotes a ferromagnetic component; B denotes the phase change component; C denotes a manganese compound component; x denotes the total atomic percentage of A, wherein 1%≦x≦40%, y denotes the total atomic percentage of B, wherein 40%≦y≦98%, and z denotes the total atomic percentage of C, wherein 1%≦y≦20%.
 39. The phase change magnetic material of claim 37, wherein A is selected from the group consisting of Co, Fe Ni and Fe—Pt, and B is selected from the group consisting of Ge—Sb—Te, Ge—Te, GeSb, InSbTe, Sb₇₀Te₃₀, Sb₂Te₃, Sb, Te and Ag—In—Sb—Te.
 40. The phase change magnetic material of claim 37, selected from the group consisting of Co_(6.3) Ge_(31.1) Sb_(27.1)Te_(35.5), Co_(3.6) Ge_(20.8) Sb_(30.5)Te_(44.9), Co_(2.8) Ge_(17.9) Sb_(31.9)Te_(47.1), Co_(6.1) Ge_(14.3) Sb₃₃Te_(46.5), Co_(3.0) Ge_(18.5) Sb_(30.1)Te_(48.2), Co_(5.0) Ge_(16.9) Sb_(31.6)Te_(46.5), Co_(1.5) Ge_(17.3) Sb_(32.9)Te_(48.3), Co_(5.4) Ge_(17.2) Sb_(30.5)Te_(46.9), Co_(2.0) Ge_(17.7) Sb_(32.5)Te_(47.8), Co_(5.8) Ge_(17.1) Sb_(32.3)Te_(44.8), Co_(4.6) Ge_(14.9) Sb_(33.4)Te_(47.1), Co_(10.1) Ge_(14.4)Sb_(34.6)Te_(40.9), Co_(26.1) Ge_(17.2) Sb_(22.1)Te_(34.6), Co_(5.6)Ge_(15.8)Sb_(33.6)Te₄₅, Fe_(20.2) Ge_(21.5) Sb_(16.9) Te_(41.4), Fe_(9.2) Ge_(16.3) Sb_(27.4) Te_(47.2), Fe_(4.7) Ge_(18.5) Sb_(28.1) Te_(48.6), Fe_(4.4) Ge_(14.8) Sb_(34.2) Te_(46.6), Fe_(11.1) Ge₁₆ Sb_(25.9) Te_(47.1), Fe_(1.0) Ge_(15.7) Sb_(35.2) Te_(48.2), Fe_(7.2) Ge_(14.7) Sb_(32.9) Te_(45.2), Fe_(28.2) Pt_(32.4) Ge_(30.0) Te_(9.3), Fe_(4.1) Pt_(4.2) Ge_(64.5) Te_(27.1), Fe_(2.1) Pt_(5.5) Ge_(63.9) Te_(28.4), Fe_(1.1) Pt_(2.7) Ge_(64.3) Te_(31.9), Fe_(4.6) Pt_(7.3) Ge_(59.5) Te_(28.6), Fe_(5.0) Pt_(6.8) Ge_(59.6) Te_(28.6), Fe_(1.1) Pt_(1.1) Ge_(50.4) Te_(31.1), Fe_(4.8) Pt_(4.6) Ge_(58.2) Te_(32.4), Fe_(1.2) Pt_(2.5) Ge_(54.2) Te_(41.9), and Fe_(1.0)Pt_(2.0)Ge_(62.1) Te_(34.9).
 41. The phase change magnetic material of claim 24, wherein the similar crystal structure of the material is at least substantially similar to the phase change material component.
 42. The phase change magnetic material of claim 24, wherein the unit cell of the crystal structure of the material comprises at least one atom of the phase change material component and at least one atom of the magnetic material component.
 43. The phase change magnetic material of claim 24, wherein said material is synthesized by a method selected from laser ablation, laser synthesis, sputtering, ion plating, chemical vapor deposition (CVD), plasma enhanced chemical vapor, metal organic chemical vapor deposition, spin coating, molecular beam epitaxy, top-seeded solution growth, thermal pressing, vacuum melting, and crystal growth.
 44. A device comprising the phase change magnetic material of claim 24 wherein the device is selected from optical media, phase change random access memory (PCRAM) devices, magnetic random access memory (MRAM) devices, solid state memory devices, sensor devices, logical devices, artificial neuron network, cognitive devices, three level device, control device, SOC device and semiconductors.
 45. A phase change magnetic composite material for use in optical media, phase change random access memory (PCRAM) devices, magnetic random access memory (MRAM) devices, solid state memory devices, sensor devices, logical devices, cognitive devices, artificial neuron network, three level device, control device, SOC device, and semiconductors, said material, comprising: a phase change material component, and a ferromagnetic material component, wherein said material exhibits both magnetic effects and phase change effects.
 46. A homogeneous optical recording medium for recording information, said medium comprising a phase change material component, and a ferromagnetic material component, wherein said phase change magnetic composite material has a single crystalline phase associated therewith a first magnetic property and a first phase change property, wherein the atoms of magnetic materials have replaced the atoms of phase change materials in the unit cell of the phase change material, without destroying/disrupting its crystal structure, and an amorphous phase associated therewith a second magnetic property and a second phase change property such that when the material undergoes phase change from crystalline phase to amorphous phase, the material exhibits a corresponding change in both its phase change properties and its magnetic properties.
 47. The phase change magnetic material of claim 38, wherein A is selected from the group consisting of Co, Fe Ni and Fe—Pt, and B is selected from the group consisting of Ge—Sb—Te, Ge—Te, GeSb, InSbTe, Sb₇₀Te₃₀, Sb₂Te₃, Sb, Te and Ag—In—Sb—Te. 